Photodisintegration of lithium isotopes

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Date

2010-08

Author

Wurtz, Ward Andrew

Type

Thesis

Degree Level

Doctoral

Abstract

We have performed a measurement of the photodisintegration of the lithium isotopes, 6Li and 7Li, using a monochromatic, polarised photon beam and a segmented neutron detector array which covers approximately 1/4 of 4ƒÎ srad. Using time-of-flight and scintillator light-output spectra we separate the data into individual reaction channels. This work is motivated by the need to compare with recent theoretical predictions and to provide data for future theoretical work.
For the photodisintegration of 6Li we took data at 12 photon energies between 8 and 35 MeV. We describe the data using a model consisting of two-body reaction channels and obtain angular distributions and absolute cross sections for many of these reaction channels. We compare our results with a recent Lorentz integral transform calculation (Bacca et al. Phys. Rev. C 69, 057001 (2004)). Our results are in reasonable agreement with the calculation, in contradiction with previous experimental results.
For the photodisintegration of 7Li, we took data at 9 photon energies between 10 and 35 MeV. We obtain cross sections for the reaction channel 7Li + ƒÁ ¨ n + 6Li(g.s.) at all photon energies with angular distributions at all but the highest energy. We obtain angular distributions and total cross sections for reaction channels involving excited states of the daughter nucleus, 6Li, at select energies. We hope that these measurements will provide incentive for new theoretical calculations.
We observe neutrons that can only be described by the reaction channel 7Li+ƒÁ ¨ n+6Li(10.0) which necessitates an excited state of 6Li with excitation energy Ex = 10.0 } 0.5 MeV that is not in the standard tables of excited states.